Self-aligning mud pump assembly

ABSTRACT

A self-aligning mud pump apparatus is provided. In one embodiment, the mud pump includes a rotatable crankshaft, a crosshead, a crosshead guide, and a hub disposed in a housing. The hub is disposed on the crankshaft and is operable to convert rotating motion of the crankshaft to reciprocating motion of the crosshead within the crosshead guide. The hub is coupled to the crosshead via a connecting rod, which is connected the crosshead such that the connecting rod has five degrees of freedom with respect to the crosshead guide. The mud pump may also or instead include a piston coupled to the crosshead with five degrees of freedom between the piston and the crosshead. Additional systems, devices, and methods are also disclosed.

BACKGROUND

This section is intended to introduce the reader to various aspects ofart that may be related to various aspects of the presently describedembodiments. This discussion is believed to be helpful in providing thereader with background information to facilitate a better understandingof the various aspects of the present embodiments. Accordingly, itshould be understood that these statements are to be read in this light,and not as admissions of prior art.

In order to meet consumer and industrial demand for natural resources,companies often invest significant amounts of time and money in findingand extracting oil, natural gas, and other subterranean resources fromthe earth. Particularly, once a desired subterranean resource such asoil or natural gas is discovered, drilling and production systems areoften employed to access and extract the resource. These systems may belocated onshore or offshore depending on the location of a desiredresource. Further, such systems generally include a wellhead assemblymounted on a well through which the resource is accessed or extracted.These wellhead assemblies may include a wide variety of components, suchas various casings, valves, pumps, fluid conduits, and the like, thatcontrol drilling or extraction operations.

As will be appreciated, drilling and production operations employ fluidsreferred to as mud or drilling fluids to provide lubrication and coolingof the drill bit, clear away cuttings, and maintain desired hydrostaticpressure during operations. Mud can include all types of water-based,oil-based, or synthetic-based drilling fluids. Mud pumps can be used tomove large quantities of mud from surface tanks, down thousands of feetof drill pipe, out nozzles in the bit, back up the annulus, and back tothe tanks. Operations come to a halt if the mud pumps fail, and thus,reliability under harsh conditions, using all types of abrasive fluids,is of utmost commercial interest.

SUMMARY

Certain aspects of some embodiments disclosed herein are set forthbelow. It should be understood that these aspects are presented merelyto provide the reader with a brief summary of certain forms theinvention might take and that these aspects are not intended to limitthe scope of the invention. Indeed, the invention may encompass avariety of aspects that may not be set forth below.

Some embodiments of the present disclosure generally relate to aself-aligning mud pump apparatus. In one embodiment, the self-aligningmud pump apparatus includes a housing and a rotatable crankshaftdisposed in the housing. The self-aligning mud pump apparatus caninclude a crosshead disposed in the housing, as well as a crossheadguide disposed in the housing to constrain movement of the crosshead.The self-aligning mud pump apparatus can include a hub disposed in thehousing and disposed on the crankshaft for converting a rotating motionof the crankshaft to a reciprocating motion of the crosshead via aconnecting rod having a first end coupled to the hub and a second endcoupled to the crosshead. The connecting rod can be coupled to thecrosshead such that the connecting rod has five degrees of freedom withrespect to the crosshead guide.

Certain embodiments of the present disclosure generally relate to amethod for assembling self-aligning components of a pump. The method caninclude providing a crosshead of the pump and coupling a connecting rodto the crosshead with a first socket joint that allows three rotationaldegrees of freedom between the connecting rod and the crosshead. Themethod can also include coupling a piston to the crosshead with a secondsocket joint that allows three rotational degrees of freedom between thepiston and the crosshead.

Various refinements of the features noted above may exist in relation tovarious aspects of the present embodiments. Further features may also beincorporated in these various aspects as well. These refinements andadditional features may exist individually or in any combination. Forinstance, various features discussed below in relation to one or more ofthe illustrated embodiments may be incorporated into any of theabove-described aspects of the present disclosure alone or in anycombination. Again, the brief summary presented above is intended onlyto familiarize the reader with certain aspects and contexts of someembodiments without limitation to the claimed subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects, and advantages of certain embodimentswill become better understood when the following detailed description isread with reference to the accompanying drawings in which likecharacters represent like parts throughout the drawings, wherein:

FIG. 1 generally depicts a wellsite system, in accordance with one ormore implementations described herein.

FIG. 2 shows a side cutaway view of a prior art pump.

FIG. 3 shows a schematic of a mud pump in accordance with one or moreimplementations described herein.

FIG. 4A shows a schematic of an alternative mud pump in accordance withone or more implementations described herein.

FIG. 4B shows a schematic of an alternative mud pump in accordance withone or more implementations described herein.

FIG. 4C shows a schematic of an alternative mud pump in accordance withone or more implementations described herein.

FIG. 5A shows a schematic of a crankshaft of a mud pump in accordancewith one or more implementations described herein.

FIG. 5B shows a cross-section of a lubricated pad, as an alternative fora roller bearing, for use in conjunction with the crankshaft of FIG. 5Ain accordance with one or more implementations described herein.

FIG. 6A shows a schematic of an alternative mud pump in accordance withone or more implementations described herein.

FIG. 6B shows a schematic of an alternative crankshaft of a mud pumpsuch as shown in FIG. 6A in accordance with one or more implementationsdescribed herein.

FIG. 6C shows a schematic of an alternative crankshaft of a mud pumpsuch as shown in FIG. 6A in accordance with one or more implementationsdescribed herein.

FIG. 7A shows a schematic of a modular mud pump unit that can be usedalone or in combination with a mirror-image modular unit, as shown inFIG. 7B, in accordance with one or more implementations describedherein.

FIG. 8A shows a partial cross-section of a crosshead and connecting rodinterface of a mud pump, in accordance with one or more implementationsdescribed herein.

FIG. 8B shows a schematic of the crosshead and connecting rod interfaceof FIG. 8A in accordance with one or more implementations describedherein.

FIG. 8C shows a partial cross-section of a crosshead and connecting rodinterface of a mud pump, in accordance with one or more implementationsdescribed herein.

FIG. 9A depicts a piston extending from a crosshead in accordance withone or more implementations described herein.

FIG. 9B is a section view of the crosshead and piston of FIG. 9A, inaccordance with one or more implementations described herein.

FIGS. 10A-10F depict various embodiments of a plunger piston in varioussealing configurations in accordance with one or more implementationsdescribed herein.

FIGS. 11A and 11B depict a plunger piston in a sleeve in accordance withone or more implementations described herein.

FIGS. 12A and 12B depict a discharge valve in a fluid end of a mud pumpin accordance with one or more implementations described herein.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

Specific embodiments of the present disclosure are described below. Inan effort to provide a concise description of these embodiments, allfeatures of an actual implementation may not be described in thespecification. It should be appreciated that in the development of anysuch actual implementation, as in any engineering or design project,numerous implementation-specific decisions must be made to achieve thedevelopers' specific goals, such as compliance with system-related andbusiness-related constraints, which may vary from one implementation toanother. Moreover, it should be appreciated that such a developmenteffort might be complex and time-consuming, but would nevertheless be aroutine undertaking of design, fabrication, and manufacture for those ofordinary skill having the benefit of this disclosure.

When introducing elements of various embodiments, the articles “a,”“an,” “the,” and “said” are intended to mean that there are one or moreof the elements. The terms “comprising,” “including,” and “having” areintended to be inclusive and mean that there may be additional elementsother than the listed elements. Moreover, any use of “top,” “bottom,”“above,” “below,” other directional terms, and variations of these termsis made for convenience, but does not require any particular orientationof the components.

The present disclosure describes a variety of design changes to mud pumpkinematics and construction to result in a less rigid, more robust andreliable mud pump. In a first embodiment described in greater detailbelow, load balancing is achieved by spacing hubs along the crankshaftof the mud pump with the bull gears disposed opposite one another, onthe outermost ends of the crankshaft adjacent to the housing. In such anembodiment, the hubs are disposed along the crankshaft between the bullgears. In a second embodiment described in greater detail below, a novelcrosshead design enables connection to both connecting rod and piston,resulting in self-aligning components with at least three degrees ofrotational freedom and two degrees of translational freedom. In a thirdembodiment described in greater detail below, the present disclosurealso includes various seal and/or piston sleeve assemblies that can beapplied to a plunger style piston.

Generally speaking, FIG. 1 illustrates a wellsite system in which thedisclosed mud pump can be employed. The wellsite system of FIG. 1 may beonshore or offshore. In the wellsite system of FIG. 1, a borehole 11 maybe formed in subsurface formations by rotary drilling using any suitabletechnique. A drill string 12 may be suspended within the borehole 11 andmay have a bottom hole assembly 100 that includes a drill bit 105 at itslower end. A surface system of the wellsite system of FIG. 1 may includea platform and derrick assembly 10 positioned over the borehole 11, theplatform and derrick assembly 10 including a rotary table 16, kelly 17,hook 18 and rotary swivel 19. The drill string 12 may be rotated by therotary table 16, energized by any suitable means, which engages thekelly 17 at the upper end of the drill string 12. The drill string 12may be suspended from the hook 18, attached to a traveling block (notshown), through the kelly 17 and the rotary swivel 19, which permitsrotation of the drill string 12 relative to the hook 18. A top drivesystem could alternatively be used, which may be a top drive system wellknown to those of ordinary skill in the art.

In the wellsite system of FIG. 1, the surface system may also includedrilling fluid 26 (also referred to as mud) stored in a pit/tank 27 atthe wellsite. A pump 29 supported on a skid 28 may deliver the drillingfluid 26 to the interior of the drill string 12 via a port in the swivel19, causing the drilling fluid to flow downwardly through the drillstring 12 as indicated by the directional arrow 8. The drilling fluid 26may exit the drill string 12 via ports in a drill bit 105, and circulateupwardly through the annulus region between the outside of the drillstring 12 and the wall of the borehole 11, as indicated by thedirectional arrows 9. In this manner, the drilling fluid 26 lubricatesthe drill bit 105 and carries formation cuttings up to the surface, asthe drilling fluid 26 is returned to the pit/tank 27 for recirculation.The drilling fluid 26 also serves to maintain hydrostatic pressure andprevent well collapse. The drilling fluid 26 may also be used fortelemetry purposes. A bottom hole assembly 100 of the wellsite system ofFIG. 1 may include logging-while-drilling (LWD) modules 120 and 120Aand/or measuring-while-drilling (MWD) modules 130 and 130A, aroto-steerable system and motor 150, and the drill bit 105.

FIG. 2 shows a cutaway side view of a prior art mud pump, illustratingvarious components of the power assembly, the portion of the pump thatconverts rotational energy into reciprocating motion. A pump as shown inFIG. 2 could be used as pump 29 of FIG. 1, although many other mudpumps, including those with designs described below in accordance withcertain embodiments of the present technique, could instead be used aspump 29. Pinion gears 52 along a pinion shaft 48 drive a larger gearreferred to as a bull gear 42 (e.g., a helical gear or a herringbonegear), which rotates on a crankshaft 40. Pinion shaft 48 is turned by amotor (not shown). The crankshaft 40 turns to cause rotational motion ofhubs 44 disposed on the crankshaft 40, each hub 44 being connected to orintegrated with a connecting rod 46. By way of the connecting rods 46,the rotational motion of the crankshaft 40 (and hub 44 connectedthereto) is converted into reciprocating motion. The connecting rods 46couple to a crosshead 54 (a crosshead block and crosshead extension asshown may be referred to collectively as the crosshead 54 herein). Thecrosshead 54 moves translationally constrained by guide 57. Pony rods 60connect the crosshead 54 to a piston 58. In the fluid end of the pump,each piston 58 reciprocates to move mud in and out of valves in thefluid end of the pump 29.

Using conventional mud pump designs, pumping drilling fluids at above50% capacity and/or for longer periods of time accelerates pump failure.With any combination of the design changes described below implemented,a mud pump may be operable at a higher capacity for longer periods oftime. The design changes disclosed herein include load balancingembodiments, self-aligning power assembly embodiments, and pistonsealing implementations.

Turning now to FIG. 3, a load-balanced mud pump is shown. Within ahousing 33, a pinion shaft 48 is disposed, supported in roller bearings51 at each opposing end of pinion shaft 48. Pinion shaft 48 is driven bya motor (not shown). A pair of pinion gears 52 rotate on the pinionshaft 48. Pinion gears 52 engage with bull gears 42, each of whichrotate on a crankshaft 40. As can be seen in FIG. 3, the bull gears 42are positioned adjacent to the housing 33 along the crankshaft 40, andpinion gears 52 are likewise positioned adjacent to the housing 33 alongthe pinion shaft 48. A plurality of hubs 44 are positioned along thecrankshaft 40 between the bull gears 42 without any hubs positionedbetween the bull gears 42 and the walls of the housing 33.

By separating the largest, heaviest gears, i.e., the bull gears 42,toward the exterior along the crankshaft, an optimized load balance isaccomplished. The position of the pinion gears 52 being substantiallytoward the exterior along the pinion shaft 48 further contributes to theload balance of the pump overall. In other embodiments, pinion gears 42and bull gears 52 may be positioned further away from the walls of thehousing while still remaining closer to the walls of the housing than toa midpoint along the pinion shaft 48 and crankshaft 40 respectively.

Each hub 44 is integrated with a connecting rod 46 (typically a forgedmetal) that couples at an interface to a crosshead 54, which will bediscussed in further detail below. In turn, each crosshead 54 alsocouples at another interface to a plunger piston 58 (shown in FIG. 9A).Crosshead 54 is constrained in direction of movement by a guide, notshown in FIG. 3, discussed further below. In the fluid end, plungerpiston 58 draws mud in and out by way of inlet 59 and outlet 61. Valvepots 63 are the machine openings to the fluid end of the mud pump.

FIG. 4A shows a schematic of a mud pump in accordance with one or moreimplementations described herein. Motors 31 couple operatively to aseries of gear wheels 32. The gear wheels 32 rotate the pinion shaft 48.Pinion shaft 48 is supported in the housing 33 by a pinion shaft rollerbearing 51 in the wall of housing 33 at either end of the pinion shaft48. The pinion gears 52 are rotatable on pinion shaft 48. Pinion gears52 engage bull gears 42, which are rotatable on the crankshaft 40.Crankshaft 40 is supported in the housing 33 on crankshaft rollerbearings 56 in the walls of housing 33 at either end of the crankshaft40. Bull gears 42 are positioned along crankshaft 40 at opposite ends ofthe crankshaft 40, adjacent to the walls of housing 33. Hubs 44 arepositioned along the crankshaft between the bull gears 42. In theembodiment shown, the hubs 44 are spaced about evenly across thecrankshaft 40. The crankshaft 40 passes through not the center of eachhub, but at a position radially offset from the center of each hub, suchthat the hubs 44 are out of phase relative to one another to drive thepistons. Alternatively, embodiments are envisioned in which spacing isoptimized for load balancing based on the weight and/or size of eachindividual hub 44 and connecting rod 46. Additionally, four hubs 44 areshown in FIG. 4A, though pumps having as few as two, or as many as five,hubs for driving reciprocal motion of crossheads are likewisecontemplated in the present disclosure.

FIG. 4B shows a schematic of an alternative of a mud pump in accordancewith one or more implementations described herein. Motors 31 coupleoperatively to a series of gear wheels 32. The gear wheels 32 rotate twoseparate pinion shafts, denoted pinion shafts 48A and 48B in FIG. 4B.Separate pinion shafts 48 enable easier repair of pump components, asthere is sufficient room to, if needed, remove each pinion shaftindependently. By comparison a single longer length pinion shaft may beof such a length as to be physically difficult to remove once the pumpis rigged up in limited space at a wellsite. Pinion shafts 48 aresupported in the housing 33 by at least a pair of pinion shaft rollerbearings 51A and 51B in the wall of housing 33 on both sides of thehousing 33. In order for each pinion shaft to rotate without wobblingunder weight, at least two points of mechanical support are used. Thus,a mechanical support 55 affixed to (or integrated with) the housing 33provides support to pairs of roller bearings 51A and 51B. A pinion gear52 is rotatable on each separate pinion shaft 48. Pinion gears 52 engagebull gears 42, each of which is rotatable on the crankshaft 40. Thepositioning of the bull gears 42 and hubs 44 along the crankshaft 40are, in FIG. 4B, similar to the configuration as described with respectto FIG. 4A.

FIG. 4C shows a schematic of an alternative of a mud pump in accordancewith one or more implementations described herein. Motors 31 coupleoperatively to a series of gear wheels 32. The gear wheels 32 rotate twoseparate pinion shafts 48 coupled together at a coupler 65. The coupler65 serves two purposes. First, the coupler 65 mechanically fastens thetwo pinion shafts 48 to one another such that the length of the fastenedpinion shafts 48 is mechanically supported. Second, the coupler 65serves to synchronize rotation of pinion shafts 48A and 48B, allowingthe pinion shafts 48A and 48B to be rotated with respect to one anotherduring assembly for proper rotational phase difference between the hubs44 of the two shafts to drive the pistons. By disconnecting the coupler65, each pinion shaft 48 can be replaced independent of the other.Pinion shafts 48 are supported in the housing 33 by at least a pair ofpinion shaft roller bearings, denoted 51A and 51B, in the wall ofhousing 33 on both sides of the housing 33. As above, in order for eachpinion shaft to rotate without wobbling under weight, at least twopoints of mechanical support are used. Thus, mechanical support 55affixed to (or integrated with) the housing 33 provides an anchoringpoint for pairs of roller bearings 51A and 51B to hold up each pinionshaft 48A and 48B. A pinion gear 52 is rotatable on each separate pinionshaft 48. Pinion gears 52 engage bull gears 42, each of which isrotatable on the crankshaft 40. The positioning of the bull gears 42 andhubs 44 along the crankshaft 40 are, in FIG. 4C, similar to theconfiguration as described with respect to FIG. 4A.

In embodiments employing two independent separate pinion shafts, asshown in FIGS. 4B and 4C, the two segments of the pinion shaft 48 areindirectly rotationally coupled one to the other through the first bullgear 42, the crankshaft 40, and the second bull gear 42, respectively.In such embodiments, the two segments of pinion shaft 48 do not directlyengage one another.

FIG. 5A shows a schematic of a crankshaft of a mud pump in accordancewith one or more implementations described herein. The pinion shaft 48and pinion gear 52 may be configured as in any of the embodimentsdescribed above. As can be seen in FIG. 5A, the bull gears 42 arepositioned adjacent to the housing 33 along the crankshaft 40. Piniongears 52 may likewise be positioned adjacent to the housing 33 along thepinion shaft 48. A plurality of hubs 44 are positioned along thecrankshaft 40 between the bull gears 42. An optimized weight loadbalance is accomplished by separating the largest, heaviest gears, thebull gears 42. In the embodiment of FIG. 5A, the crankshaft 40 spans alength less than the width of the housing 33. In lieu of roller bearings56 in the walls of the housing 33 to support the crankshaft 40,mechanical supports 62 are attached to (or integrated with) the housing33 to support the crankshaft 40. Lubricated pads 64 affix to themechanical supports 62 so that the crankshaft 40 rotates freely. FIG. 5Bshows a cross-section of an example of a lubricated pad, as analternative for a roller bearing, for use in the embodiment shown inFIG. 5A. The lubricated pad 64 may include a lower pad 64A and an upperpad 64B, each conformed to curve around crankshaft 40. In a preferredembodiment, the lubricated pads are offset by 30° relative to ahorizontal plane running through the crankshaft 40, as shown. Thesurface of lower pad 64A and upper pad 64B are lubricated. Additionallubricant can be added to the surfaces in contact with the crankshaft 40in the gap between lower pad 64A and upper pad 64B.

FIG. 6A shows a schematic of an alternative of a mud pump in accordancewith one or more implementations described herein. Load balancing isachieved in the embodiment of FIG. 6A by positioning the bull gears 42adjacent to one another, centered on the crankshaft 40 and having noneof the hubs 44 positioned on the crankshaft 40 therebetween. Motors 31couple operatively to a series of gear wheels 32. The gear wheels 32rotate pinion shaft 48. Pinion shaft 48 is supported in the housing 33by pinion shaft roller bearings 51 in the walls of housing 33 on bothsides of the housing 33. Pinion gears 52A and 52B are rotatable onpinion shaft 48, and are positioned adjacent to one another withoutengaging one another. The pinion gears 52A and 52B may be helical indesign, as shown in FIG. 6B. Pinion gears 52 engage bull gears 42, eachof which is rotatable on the crankshaft 40. In the embodiment of FIG.6A, the crankshaft 40 spans a length less than the width of the housing33. In lieu of roller bearings 56 in the walls of the housing 33 tosupport the crankshaft 40, mechanical supports 62 are attached to orintegrated with the housing 33 to brace or support the crankshaft 40,and lubricated pads 64, such as those shown in FIG. 5B, affix to themechanical supports 62 such that the crankshaft 40 rotates freely.

In the embodiment shown in FIG. 5A, four hubs 44 are shown, and threemechanical supports 62 are shown between the hubs 44. In the embodimentshown in FIG. 6A, four hubs 44 are shown and four mechanical supports 62are shown. As with the previously described embodiments, pumps having asfew as two, or as many as five, hubs are likewise contemplated in thepresent disclosure, along with a number of mechanical supports toadequately support the weight of the hubs 44 along the crankshaft 40, ascan be readily determined by one of ordinary skill in the art.

FIG. 6C illustrates an alternative embodiment, having bull gears 42centered along the crankshaft relative to the walls of the housing 33,with hubs 44 disposed along crankshaft 40 axially away from each of thebull gears 42. Mechanical supports 62 extend from the housing 33 topositions between hubs 44. Any numerical combination of hubs andmechanical supports is contemplated by the present disclosure, to theextent that the mechanical supports 62 adequately bear the load of thecrankshaft bearing the bull gears 42 and hubs 44. The load is balancedacross the length of the crankshaft so as to minimize wobble during highor full capacity usage of the pump.

FIG. 7A shows a schematic of a modular unit that, when coupled with amirror-image modular unit, is operable as a mud pump in accordance withone or more implementations described herein. By providing independentmodules of mud pump power end components, the overall mud pump isscalable. Expensive downtime is reduced with quick repair byinterchanging modules, should any component in one module fail. Theinterchangeable mud pump module shown in FIG. 7A is contained within ahousing 33, and a mechanical support 55 is affixed to (or integratedwith) the housing 33. A crankshaft 40 is disposed within the housing 33,and a pinion shaft 48 is disposed within the housing 33. A first end ofthe crankshaft is adapted to couple rotatably to a crankshaft of asecond adjacent mud module (which would be coupled at the right side ofFIG. 7A). The second end of the crankshaft is rotatably supported in thehousing 33, such as by mechanical supports 62 having lubricated pads 64about the crankshaft 40. As shown, the crankshaft 40 has a plurality ofhubs 44 and a bull gear 42 disposed thereon. The bull gear 42 ispositioned at the second end of the crankshaft adjacent the housing 33,opposite the end of the crankshaft 40 that is supported in the wall ofthe housing 33. The mud pump module can also include a rotatable pinionshaft 48 for driving the crankshaft 40. The pinion shaft 48 has disposedthereon a pinion gear 52 engaging the bull gear 42 on the crankshaft 40.When a module such as shown in FIG. 7A is coupled to another that isconfigured as a mirror image of the one shown in FIG. 7A (as seen inFIG. 7B), a scalable, load-balanced mud pump that is easily repaired isachieved. With a smaller footprint and less weight, substantially lesseffort is used in rig-up as well. FIG. 7B shows the crankshaft 40 ofeach module coupled together with a coupler 65. Coupler 65 serves toboth provide mechanical strength where the coupler 65 fastens the twocrankshafts 40 together, as well as serving to synchronize the rotationthereof, and allow rotation of the crankshafts relative to one anotherto position each of the hubs 44 properly out of phase with respect toone another for driving the pistons.

A further improvement upon the mud pump design addresses the overallrigidity of the components about the crosshead. When the connection ofthe connecting rod or piston to the crosshead is not in properalignment, premature wear may occur on these components, leading to pumpfailure. By implementing the kinematics of the present disclosure, fivedegrees of freedom of movement between the connecting rod and thecrosshead guide can be achieved: three degrees of rotational freedom andtwo degrees of translational freedom. Rather than a simple cylindricalpin to couple the connecting rod to the crosshead, the presentdisclosure envisions a crosshead as shown in FIGS. 8A and 8B having apin 75A with a spherical main body 75B seated in a bearing to secure theconnecting rod within the crosshead block.

FIG. 8A shows a cutaway cross-section of the crosshead and connectingrod interface, in accordance with one or more implementations describedherein. In some instances, a crosshead comprises a block that theconnecting rod end is inserted into or about, with the connecting rodheld rigidly in place by a cylindrical pin through the connecting rodand crosshead. By comparison, the crosshead design of the presentdisclosure offers additional degrees of freedom of movement. Turning nowto FIG. 8A, guides 57 hold the crosshead 54 in place for reciprocatingmotion. Crosshead 54 comprises a crosshead top 54T, a crosshead bottom54B, and crosshead side plates 54S. Connecting rod 46 is inserted intothe crosshead 54 and secured in place by a pin 75A having a sphericalmain body 75B. The spherical main body 75B may be integrated with a pin,or a sphere component may be placed about a cylindrical pin. The ends ofpin 75A engage with crosshead side plates 54S to hold pin 75A in placewhile connecting rod 46 is engaged with the cross head 54. A two-piecebearing 76 fastened about the spherical main body 75B of pin 75Afacilitates swiveling motion of the connecting rod 46 about the pin 75A.Crosshead side plates 54S secure in place via screws (or like fasteners)through holes 74 in crosshead side plates 54S after the connecting rod46, bearing 76, and pin 75A are inserted in the crosshead 54. A braceplate 54C provides structural reinforcement to the pin 75A when securedin place to crosshead side plates 54S with fasteners through screw holes74.

Pin 75A having a spherical main body 75B allows for rotational movementin the R_(X), R_(Y), and R_(Z) directions (defined with Y-axis in thedirection of reciprocal motion into the page), in that connecting rod 46is free to move rotationally about the spherical main body 75B of thepin 75A. Such freedom of movement is facilitated by bearing 76. FIG. 8Bshows a cutaway profile of the crosshead and connecting rod interface ofFIG. 8A. As can be seen, the connecting rod 46 includes two apertures,the larger of which is engaged about a hub 44 on the crankshaft 40, andthe smaller of which fits into the crosshead 54 that reciprocatesthrough guide 57. Employing the pin 75A having a spherical main body75B, the connecting rod 46 with bearing 76 is free to swivel about thepin 75A, thereby achieving three degrees of rotational freedom in theR_(X), R_(Y), and R_(Z) directions.

Turning to FIG. 8B, at least two degrees of translational freedom areachieved between the connecting rod 46 and the crosshead guide 57.Translational movement in the direction T_(Y) is the intentionalreciprocating movement of the assembly to move the piston. Keys 66 keepcrosshead 54 aligned with guide 57 during reciprocating motion.Returning to FIG. 8A, a gap is defined between the crosshead side plates54S and bearing 76, providing sufficient freedom in the design fortranslational movement of the connecting rod 46 within the crosshead 54in the T_(X) direction along the X-axis. In some embodiments, thespherical main body 75B may slide along pin 75A when the components arephysically separate parts; alternatively, in embodiments in which thespherical main body 75B is integral to pin 75A, the pin 75A may beconfigured to translate along its axis between side plates 54S.

Turning to FIG. 8C, another embodiment demonstrating at least twodegrees of translational freedom of the connecting rod 46 with respectto the crosshead guide 57 is shown. Separate pieces of bearing 76 can beseen clearly, providing spherical seating for spherical main body 75B ofpin 75A. In assembly, pieces of bearing 76 can be fastened aboutspherical body 75B of pin 75A (e.g., with a fastener extending throughtabs of the bearing 76 and the connecting rod 46, as shown at the top ofFIG. 8C). Ends of pin 75A are shown engaged with the crosshead sideplates 54S. Variable gaps intentionally imposed between bearing 76 andcrosshead side plates 54S, as well as between bearing 76 and connectingrod 46, provide sufficient design latitude for incorporating a degree ofmechanical give for translational movement of the connecting rod 46 inthe T_(X) direction, as denoted by the double-sided arrow.

In a still further embodiment, FIG. 9A shows an illustration of acrosshead and piston interface in accordance with one or moreimplementations described herein. The end of piston 58 that connects tothe crosshead 54 may be formed as a spherical knob. In one embodiment,the spherical knob may be integral to the piston 58; alternatively, thespherical knob may be a separate component fastened to the piston 58.Optionally, the piston 58 may have a sleeve 93 disposed thereon, so asto vary the effective diameter of the piston 58, which will be discussedfurther below. Turning to FIG. 9A, the knob of piston plunger 58reciprocates along the Y-axis, forced by movement of crosshead 54, wherespherical knob 90 of plunger piston 58 is enclosed in the crosshead 54.FIG. 9B shows a cutaway of the crosshead and piston interface shown inFIG. 9A. A lubrication channel 106 into the interior of the fluid-endside 92 of the crosshead 54 delivers lubricant to the spherical knob 90of plunger piston 58. A bearing 107 further facilitates rotationalmovement. In an embodiment, the bearing 107 comprises more than onebearing component having a spherical seat to receive the spherical knob90 of plunger piston 58, each of the bearing components of bearing 107being configured to fasten together about the spherical knob 90 ofplunger piston 58 in assembly. Thus, five degrees of freedom of movementare provided between the crosshead 54 and the plunger piston 58 in thefluid-end side 92 of the crosshead 54: the plunger piston 58 is able toswivel in three rotational directions with respect to the crosshead dueto the spherical knob 90, and translational movement is permitted in theT_(X) and T_(Z) directions due to intentional play between the bearing107 and crosshead housing.

A further improvement upon the mud pump design addresses the issue ofseal failure about the piston. In some embodiments of mud pumps, apiston having a moveable sealing head at the fluid end is employed.However, failure of the mud pump occurs when the seal erodes in theharsh working conditions, or when the sealing head fails, such as bybreaking off. As an alternative, the present disclosure describes aheadless plunger piston having a seal 101 (and optionally sleeve 93)disposed about the piston 58. A variety of means are disclosed formonitoring the seal 101. Additionally, the sleeve 93 may be variable insize depending on the pumping pressure desired in a given application.

Turning now to FIG. 10A, plunger piston 58 is shown in detail, withreciprocating motion in the T_(Y) direction. A directional seal 101 isdisposed about the plunger piston 58 on the fluid end. A lubricated pad94 is provided at the power end of the plunger piston 58, to which oilmay be reapplied to lubricate the plunger piston 58. In a cavity 95defined between the seal 101 and the lubricated pad 94, a drain port 96may be included so that the quality of the seal 101 at the fluid end canbe monitored. As the seal 101 fails, mud will leak in under and aroundthe seal 101, and empty out of the drain port 96.

In an alternative embodiment, as shown in FIG. 10B, a lubricated pad 94is provided at the power end of the plunger piston 58. Similar to asshown in FIG. 10A, in a cavity 95 formed between the seal 101 and thelubricated pad 94, a drain port 96 may be included so that the qualityof the seal 101 at the discharge end can be monitored. Additionally, aninjection port 98 to the cavity 95 may be provided such that water canbe injected into the cavity to flush any leakage mud out of the drainport 96. In an embodiment, the water may be injected at a relatively lowpressure. As the seal 101 fails, mud will leak in under and around theseal, and be forcibly flushed by the injected water out of the drainport 96. The injected water also serves to clean and protect the wettedarea of the plunger piston 58.

In an alternative embodiment, as shown in FIG. 10C, a lubricated pad 94is provided at the power end of the plunger piston 58, as in previousembodiments. An oil port 100 allows lubricant to be added, while an oildrain 102 allows lubricant to flush out, keeping the surface of thepiston 58 continually renewed with lubricant. This embodiment is alsodepicted as having a cavity 95, drain port 96 and injection port 98, asdescribed above. The lubricated pad 94 can be optionally isolated fromthe area where mud leakage may be present by an additional directionalseal 97 that is not in contact with the pressurized mud in the fluidend. The flow and temperature of oil lubricant added may or may not becontrolled.

In an alternative embodiment, as shown in FIG. 10D, a lubricated pad 94is provided at the power end of the plunger piston 58. An oil port 100allows lubricant to be added through cavity 103 to the lubricated pad94, while an oil return 104 allows lubricant to circulate, keeping thesurface of the plunger piston 58 continually renewed with lubricant. Theoil return 104 enables control of the temperature of the lubricant, byinclusion of a heat exchanger 110 to cool the oil. The heat exchanger110 employed may be of any type familiar to one of ordinary skill in theart. Cavity 95 is defined between seal 101A and an additionaldirectional seal 101B. Additional directional seal 97 prevents oil fromentering the fluid end from cavity 103, and mixing with any leaking mudin cavity 95. An injection port 98 to the cavity 95 may be provided suchthat water can be injected into the cavity 95 to clean the plungerpiston 58. In such an embodiment, the water may be injected at arelatively high pressure, in contrast with the low pressure injectedwater described with respect to FIG. 10C, and forcibly flush leakingfluid from cavity 95. The lubricated pad 94 is thus fluidly isolatedfrom the area around the seal 101 where mud leakage may be present. Theembodiment shown in FIG. 10D does not include a drain port 96, buthigh-pressure water injected into cavity 95 can exit past the seal 101Binto the fluid end of the pump.

An alternative embodiment, as shown in FIG. 10E, is similar to thatshown in FIG. 10D, but also includes a cavity 99 with a drain port 96.The cavity 99 is provided between the end of the seal 101A and thedirectional seal 97. The drain port 96 allows the quality of the seals101 to be monitored. Additionally, the injection port 98 and the cavity95 between the sealing elements 101A and 101B allow water to be injectedinto the cavity 95, which can aid the directional seal elements such as101B in the fluid end by providing resistance to mud leaking under theseal 101B from the working space of the pump.

In embodiments including a drain port 96, as the seals 101 fail, mud mayleak and be forcibly flushed out of the drain port 96. Injected wateralso serves to clean and protect the wetted area of the plunger piston58. When there is no mud particulate in the flow out of the drain port96, the seal 101 is in good working condition; however, when there ismud particulate in the flow out of the drain port 96, it is indicativethat the seal 101 has begun to fail.

FIG. 10F shows a detailed view of a scraper seal 112 that may be addedto the fluid-end side of a seal 101. Scraper seal 112 may be selectedfrom various known geometries of scraper or wiper styles that serve toclean the piston 58 when drawn towards the power-end of the pump.

Additionally, as the plunger piston 58 may be a headless plunger, asleeve 93 can be disposed about the piston 58. The sleeve 93 may vary inthickness, and be selected to vary the overall effective piston diameterbased on desired pressure in the mud pump. The sleeve 93 is disposedabout the plunger piston 58 at the fluid end of the plunger piston 58 influid communication with the mud. When a sleeve 93 is employed, the seal101 and lubricating pad 94 are disposed about the sleeve 93 positionedabout the piston 58. In each of the embodiments shown in FIGS. 10A-10E,a sleeve 93 can optionally be disposed about the piston to vary pistondiameter based on desired pressure in the fluid end of the pump.

FIG. 11A and FIG. 11B show a piston 58 having a sleeve 93 to manipulatethe overall effective diameter of the piston 58. As previously stated,changing the diameter of the piston 58 by the addition of sleeve 93 canallow variation of the pressure in the mud pump. For example, FIG. 11Ashows a first sleeve 93A that when in place about the piston 58 producesan overall diameter of 5.5 inches (approximately 14 cm). By comparison,FIG. 11B shows a second sleeve embodiment 93B that when in place aboutthe piston 58 produces an overall diameter of 8 inches (approximately 20cm).

Finally, wear and stress on components of the mud pump can be reducedduring start-up of the mud pump. FIG. 12A and FIG. 12B provideschematics of a discharge valve in a fluid end of a mud pump. Without adischarge valve in the fluid end of a mud pump, the pistons arecompressing fluid during the start-up of the mud pump, which can createunnecessary overload of the components. In such embodiments, mud pumpflow is adjusted by changing the speed of the electrical motor drivingthe mud pump. By comparison, as can be seen in FIG. 12A, a dischargevalve 108 is added to the fluid flow in the fluid end of the mud pumpbetween inlet 59 and outlet 61 (e.g., at the end of a pump liner 115).During start-up of the mud pump, the discharge valve 108 can be opened(for example, by rotation) to provide direct fluid communication betweenthe inlet 59 and the outlet 61. Such free fluid communication reducesthe load on components of the mud pump, from electrical motor 31 topiston 58. Additionally, each section of the mud pump can besubstantially instantaneously shut down to adjust flow. FIG. 12A showsdischarge valve 108 closed with fluid communication blocked indicated byarrow 109. FIG. 12B shows discharge valve 108 open with fluidcommunication freely flowing indicated at arrow 109.

While the aspects of the present disclosure may be susceptible tovarious modifications and alternative forms, specific embodiments havebeen shown by way of example in the drawings and have been described indetail herein. But it should be understood that the invention is notintended to be limited to the particular forms disclosed. Rather, theinvention is to cover all modifications, equivalents, and alternativesfalling within the spirit and scope of the invention as defined by thefollowing appended claims.

The invention claimed is:
 1. A self-aligning mud pump apparatus,comprising: a housing; a rotatable crankshaft disposed in the housing; acrosshead disposed in the housing; a crosshead guide disposed in thehousing to constrain movement of the crosshead; and a hub disposed inthe housing and disposed on the crankshaft for converting a rotatingmotion of the crankshaft to a reciprocating motion of the crossheadwithin the crosshead guide via a connecting rod having a first endcoupled to the hub and a second end coupled to the crosshead; whereinthe connecting rod is coupled to the crosshead via a bearing mounted ona retention component received in a spherical seat such that the secondend of the connecting rod pivots in three rotational degrees of freedomwithin the crosshead and the connecting rod has two translationaldegrees of freedom with the crosshead guide; wherein the retentioncomponent is fixedly coupled to a pin, and the pin is moveably coupledto the crosshead so as to allow the pin, along with the retentioncomponent, the bearing, and the connecting rod to translate together ina direction perpendicular to the direction of reciprocating motion ofthe crosshead within the crosshead guide.
 2. The mud pump apparatusaccording to claim 1, wherein play between the bearing and theconnecting rod allows the second end of the connecting rod to translatewith respect to the bearing in a direction perpendicular to thedirection of reciprocating motion of the crosshead within the crossheadguide.
 3. The mud pump apparatus according to claim 1, furthercomprising a plunger piston coupled to the crosshead with five degreesof freedom between the plunger piston and the crosshead.
 4. The mud pumpapparatus according to claim 3, wherein the five degrees of freedombetween the plunger piston and the crosshead include three rotationaldegrees of freedom and two translational degrees of freedom.
 5. The mudpump apparatus according to claim 3, wherein the plunger piston is aheadless piston and includes a spherical knob, and the crossheadincludes a socket that receives the spherical knob.
 6. The mud pumpapparatus according to claim 5, comprising a bearing including thesocket.